Method for measuring missing corner dimensions

ABSTRACT

A method for obtaining the area of a missing portion of an object under inspection with a borescope includes aligning the borescope with the object under inspection, extrapolating the missing edges of the missing portion and calculating the missing portion area using the extrapolated missing edges and a defined remaining edge of the missing portion.

BACKGROUND OF THE INVENTION

The field of the invention relates to industrial borescopes andmeasurements taken therewith.

Borescopes are often used in industrial applications to inspect objectswithin machines or devices which are difficult or impractical todisassemble for inspection, such as aircraft engines or power generationturbines. U.S. Pat. No. 5,633,675 describes a borescope device having amechanism for generating and projecting a shadow on an object ofinterest. The shadow has a known projection geometry relative to thefield of view. The position of the shadow in captured images providesobject distance and magnification information which enables thedetermination of the size of other visible elements on the object ofinterest being inspected with the borescope. Other measurement methodssuch as the stereoscope approach described in U.S. patent also allowsuch size determinations.

Referring now to FIG. 1 there is shown a borescope imager head 10 housedin a small diameter housing 14. The borescope imager head 10 has a fiberoptic bundle 12 for conveying light from an illumination source outsidethe head, and a video image sensor 18 with associated optics 20 placeddistally at least a given distance from the image sensor. The light fromthe tip 42 of the fiber optic bundle 12 passes through an opticallytransparent illumination window 32 into which is set, etched, drawn orotherwise affixed an opaque object 16 that can cast a shadow either onthe target or in the plane of the target. As known in the art, the videoimage sensor 18 comprises a CCD imager 22, a hybrid circuit 26 connectedthereto by well known means such as wires, and a cable 30 for relayingthe video image detected through an optically transparent optic window33 to a monitor or other device, typically via a video processingsystem. Video processing systems can include A/D converters, digitalsignal processing and D/A conversion to generate a signal suitable foranalog monitors.

Borescope images can reveal that portions of an apparatus underinspection are damaged, such as by missing portions of the apparatus.Turbine blades, for example, do wear or can break, so that the endportions of the blades are sometimes broken off or worn from theoriginal size and shape. It is advantageous when using a boresope toinspect an apparatus to also be able to determine the size of themissing or worn portion of the apparatus under inspection. The missinglength of one or both original edges must often be known for compliancewith standards for wear and damage. Current methods for determiningmissing dimensions do not address accurately determining the length ofthe missing original edges. Current methods typically assume that edgesof a blade are perpendicular and in a single plane, which is not usuallythe case, so that measurement error is inherent when using currentmethods. It is also difficult to determine a missing area of a blade orother object corner, since two edges must be extrapolated and combinedwith the remaining missing portion edge to obtain the border of themissing area. Accurately determining the bounds of a missing portion isnot readily done using current methods.

U.S. Pat. No. 6,945,931 describes several methods for calculating themissing area of a turbine blade using a borescope. The methods requiredetermination of at least one plane relative to the blade, combined witha second plane or line, that is used to establish the boundary of theoriginal, undamaged blade. Vectors are used with points on the blade toestablish the plane perpendicular to the blade top edge. Complexcalculations are required simply to establish the position of theborescope relative to the blade for taking a measurement. The '931patent provides methods for determining area by dividing the boundariesof the missing area into smaller, geometric shape samples, for whichsamples area calculations are more easily made and then summed toproduce a whole missing area value.

The above-referenced patent describes a complex method involving theuser placement of numerous cursors to determine a missing corner area.Many maintenance specifications for turbine engines set limits on thelength of material missing along the two edges that would intersect atthe corner rather than the missing area. Thus, the referenced patentdoes not provide the information needed by inspectors, and it requiresthe placement of more cursors than are needed to determine the necessarymissing length information thus reducing the efficiency of suchmeasurements. Accordingly, a need exists for an improved measurementsystem which more quickly and efficiently provides a more accuratemissing corner measurement, in particular, one which provides ameasurement of the length and/or depth of the missing area bounds.

BRIEF DESCRIPTION OF THE INVENTION

According to an embodiment of the invention, a method of measuringmissing corner dimensions of an object under inspection with a borescopeis provided. Using a shadow-type probe, the shadow is aligned with theobject under inspection to provide a frame of reference. The viewmagnification of the object under inspection via the probe is determinedusing the shadow. A cursor is used to mark at least two points on eachof the side and top edges of the object under inspection to identify theboundaries. One point marked on each edge is where the missing areabegins. The missing area is bounded by the intersection of the linesdefined by the two marked edges. The dimensions of the missing edgesbounded by the cursor markings and the line intersection are calculatedand provided to a user.

Alternatively, an embodiment of the invention uses a probe, such as astereoscopic probe to view the object under inspection having a missingportion and obtains the dimensions of the missing portion. The probe isaligned with the object under inspection to view a region of the objectincluding the missing portion and then the cursor is used to mark thepoints on the remaining edges, and dimensions are obtained as in theprior embodiment.

In a further embodiment of the invention, an inspection probe is used toview an object having a missing portion with a boundary which does notlie entirely in one plane. The probe is aligned with the object underinspection to view the missing portion, and then the edges of the objectunder inspection are defined as described above using cursor marks. Areference plane is determined from the cursor marks, planesperpendicular to the reference plane defined by the cursor marks alongeach remaining edge are generated, and the intersection of theperpendicular planes and reference plane is identified. The missing edgedimensions are then measured using the cursor marks and intersectionpoint.

In another embodiment of the invention, three cursor marks are made. Twocursor marks define one edge, while the third cursor mark is made at thepoint where the missing portion begins on the adjacent edge. A videoprocessing unit superimposes a line extrapolated from the third cursormark to be perpendicular with a line defined by the first two cursormarks. The extrapolated line is adjusted until it aligns with theadjacent edge and intersects the line defined by the first two cursormarks at the correct angle. Measurements of the missing area dimensionsare then taken using the bounds defined by the adjusted extrapolatedline and line defined by the first two cursor marks.

In a still further embodiment, only two cursor marks are utilized, onepositioned at each remaining edge termination point on the missingportion. Lines are generated extending from each cursor point,preferably so that they intersect. The generated lines are then manuallyadjusted, such as by a borescope operator, until each aligns with theremaining edge of the side where the cursor marker origination point ispositioned. The dimensions of the missing portion can then be obtainedfrom the corrected intersection point of the generated lines and thecursor markers.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and benefits obtained by its uses, reference ismade to the accompanying drawings and descriptive matter. Theaccompanying drawings are intended to show examples of the many forms ofthe invention. The drawings are not intended as showing the limits ofall of the ways the invention can be made and used. Changes to andsubstitutions of the various components of the invention can of coursebe made. The invention resides as well in sub-combinations andsub-systems of the elements described, and in methods of using them.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side elevation of a prior art shadow probe typeborescope;

FIG. 2 is a schematic diagram of a borescope used with embodiments ofthe invention;

FIG. 3 is a front elevation view illustrating an intact turbine bladeend;

FIG. 4 is a is a front elevation view diagramming a measurement fordetermining the dimensions of a missing corner of the turbine blade ofFIG. 3 in accordance with an embodiment of the invention;

FIG. 5 is a front elevation view diagramming a measurement in accordancewith a further embodiment of the invention;

FIG. 6 is a front elevation view of a non-planar blade diagramming ameasurement in accordance with another embodiment of the invention;

FIG. 7 is an end perspective view of the non-planar blade of FIG. 6; and

FIG. 8 is a flowchart illustrating an embodiment of the process fordetermining the area of a missing portion of the object underinspection.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings in which like reference numerals are usedto indicate the same or related elements, in FIG. 2 there is shown ageneral schematic of an embodiment of a borescope such as can be usedwith this invention. A general control box 110 containing a lightsource, external control mechanisms for use by the person handling theborescope, and internal control circuitry which is linked by electricalconnection 115 to a monitor 120. The general control box also is linkedto the borescope insertion tube 100 which ends in a borescope imagerhead 10. Other configurations are possible, such as a having a separateborescope handle containing some or all of the external and/or internalcontrols. Further, the borescope may include a processor or other deviceseparate from or as part of the internal control circuitry which is usedto identify points on a displayed image on monitor 120 and makecalculations in connection with the displayed image.

FIG. 3 illustrates a common object for inspection with a borescope suchas that described in FIG. 2—a blade 150 having blade tip 155. Blades 150are found in devices such as aircraft engines and power generationturbines as part of turbo fans, turbo jet fans, compressors andturbines, among other uses. Such blades 150 are usually subject to harshoperating conditions and require inspection to protect against failureswhich may cause severe harm. A source of defects in blades 150 is at theblade tip 155, where portions are often worn or broken off of the bladetip 155. It is important during inspections to determine the size of thedefect, so that an accurate determination whether to spend significanttime and effort to repair the blade 150 is warranted. Often, maintenancespecifications require measurement of the length or depth of a missingportion from the original blade tip or edge, respectively.

A blade 150 with a missing portion 175 of the blade tip 155 is shown inFIG. 4 with various indicia used in one embodiment to determine thedimensions and area of the missing portion 175. First, a shadow 160generated by the borescope is aligned with the blade 150 so that thearea of the missing portion 175 is in the view and shadow 160 appearsvertical in the displayed image and falls in the region of the missingportion 175. Aligning the shadow 160 in this manner indicates the probeis substantially perpendicular to the blade 150 under inspection whichis a requirement for accurate results as the entire field of view isassumed to be at the same object distance as is indicated by thehorizontal position of the shadow.

Once the probe is aligned, a user, such as a probe operator, defines theoriginal side edge 152 and blade tip 155, respectively, on an image ofthe blade 150 using cursor markers 180 a-d in at least two points oneach edge 152, 155. One cursor marker 180 a, 180 b on each edge 152, 155is positioned at the point on the edge 152, 155 where the missingportion 175 begins. These first cursor markers 180 a, 180 b define astarting measurement point for determining the length of thecorresponding missing edge 153 and 157. The borescope apparatus includesa processor or other device which generates and positions the cursormarkers 180 a-d within the image frame responsively to user input. Inthe event, for example, that the missing portion 175 was located on theother corner of blade tip 155, then cursor markers 180 a-d would beplaced on blade tip 155 and original side edge 154.

The cursor markers 180 a-d define lines 153, 157 corresponding to theboundary of the original blade 150 when the missing section 175 wasintact. The lines 153, 157 intersect at intersection 190, which definesthe extent, or bounds, of the missing portion 175. The borescopeapparatus can then be used to calculate the length of the missingportion sides between points 180 a and 190, and between points 180 b and190 using the X-Y position of the points 180 a, b, 190. That is, thelength of the missing portion along edge 152 from intersection 190 anddepth of the missing portion along blade tip 155 from intersection 190can be obtained using the cursor markers 180 a-d and intersection point190. The length and depth dimensions can then be compared, for example,with maintenance standards to determine whether repairs or replacementof the blade 150 with missing portion 175 are required, suggested, ornot necessary. Further measurements based upon knowledge of the positionof the cursor markers 180 a-d and extrapolation of intersection 190 arealso possible. Cursor markers 180 a-d thus provide a basis for aprocessor or other computing device in or connected to the borescope togenerate measurements for features of the object under inspection,including the dimensions of the missing portion 175, for display to auser via monitor 120 or other output device.

In a further embodiment of the method, after the cursor markers 180 a-dare placed, the remaining edge 158 is defined using additional cursormarkers 185 at several points along the edge 158. The cursor markers 185on the remaining edge 158 are used to define the remaining edge 158contour. The remaining edge contour and boundary 153, 157 of theoriginal blade 150 then define the missing portion 175 area. In onemethod for determining the missing portion area, the missing portion 175is subdivided into geometrically shaped sub-areas 170A, 170B, 170C, 170Dwhich have their areas more readily calculated by the borescopeapparatus. The calculations of the several areas 170A, 170B, 170C, 170Dare then summed to get the total area of missing portion 175. It shouldbe noted that the actual area of missing portion 157 can be obtainedusing either the shadow 160 as a guide to the dimensions of the missingportion area, or other dimensioning techniques known for use with othertypes of borescopes.

In a further embodiment of the invention illustrated in FIG. 5, onlythree cursor markers 180 a, 180 b and 180 c are required to initiallyidentify the bounds of the missing portion 175. Cursor markers 180 a and180 b are placed at the points where the respective remaining edges 152,155 end and the mission portion 175 begins. Cursor marker 180 c isplaced at a different point along one of the two remaining edges 152,155; in this case, cursor marker 180 c is placed on side edge 152. Line153 is then extrapolated from cursor markers 180 a and 180 c. Line 157 ais initially extrapolated from cursor marker 180 b by extending a linefrom cursor marker 180 b to be perpendicular with line 153. However, theblade tip 155 is not accurately represented by the line 157 a, as line157 a does not align with blade tip 155.

The borescope apparatus generates video overlays for a user such as aborescope operator to show the cursor markers 180 a-c and lines 153, 157relative to blade 150. The user manipulates the angle of line 157pivoting about cursor marker 180 b using the borescope controls untilthe angle of intersection Θ with line 153 is such that line 157 isaligned with blade tip 155 and accurately represents the former boundaryof the blade tip 155 in the mission portion 175. Thus, one line 153 ofthe bounds for missing portion 175 is established automatically by theplacement of cursor markers 180 a, 180 c, while the second line 157 ismanually oriented until the mission portion 175 bounds are correctlydefined. Measurements as described above can then be taken using theknown positions of the cursor markers 180 a-c and extrapolated positionof intersection 190.

In an alternate embodiment, only first cursor markers 180 a and 180 bare placed at the point where each remaining edge 152, 155, 154 ends andmissing portion 175 begins. The borescope apparatus then generates lines153, 157 from first cursor markers 180 a, 108 b, respectively.Preferably, the lines 153, 157 are generated to at least intersectinitially. The lines 153, 157 are then manipulated until the lines 153,157 correctly define the bounds of the missing portion 175, such as by auser manually aligning each line 153, 157 with the corresponding one ofthe remaining edges 152, 155, 154 either independently or simultaneouslyby adjusting the position of the line intersection. Then, as above, theintersection point 190 of the lines 153, 157 and first cursor markers180 a, 180 b are used to determine the dimensions.

FIGS. 6 and 7 illustrate a still further embodiment of the invention inwhich a blade 150 having a non-planar surface is presented forinspection and measurement of a mission portion 175 by a borescope. Asbest seen in FIG. 7, blade 150 is curved between edges 154 and 152, sothat while viewed from the top as in FIG. 6, the blade 150 appears flat.As in the embodiments described above, four cursor markers 180 a-d areplaced along remaining edges 154, 155 As shown by FIG. 7, the projectedlines 153 and 157 do not intersect in the same plane. When usingtechnologies such as stereoscopic borescopes, which yield an x,y,z spacecoordinate for each cursor, this is almost always the case.

Borescopes using two-dimensional approaches, such as shadow-typeborescopes, assume all cursor markers 180 a-d are in the same planedetermined by the shadow position. Thus, it is not necessary todetermine z positions for each cursor, since the positions are allassumed to fall mathematically in the same plane. This assumptionsimplifies the calculations but may not give results that are asaccurate as the 3-D methods yield. It will be appreciated, for example,that measurements taken from cursor markers 180 a and 180 b tointersection 190 as shown in FIG. 6, without any correction, will beerroneous due to the unrepresented angle resulting from the differencein height of the lines 153, 157 caused by the non-planar surface of theblade 150. Thus, the dimensions of the missing portion 175 cannot bemeasured to a high degree of accuracy using the methods above.

A three-dimensional solution, such as described above, is needed to bothproduce accurate measurements of the missing portion 175 bounds andaddress the mathematical issue of the points being non-planar. Aftercursor markers 180 a-d are located on a borescope image, a referenceplane 195 is determined from the three-dimensional positions of at leastthree (which would exactly define the reference plane), and preferablyall four (using curve fitting techniques), of the cursor markers 180a-d. Then, translated edge lines representative of edges 154 and 155 andtranslated points representative of cursor markers 180 a and 180 b aredefined on the reference plane. The translated edge lines and translatedpoints may be defined through various mapping techniques. One possibletechnique can be done by first identifying lines which pass throughcursor markers 180 a, 180 b, 180 c, and 180 d and are perpendicular tothe reference plane, then defining the translated points as theintersection between the lines and the reference plane. The translatededge lines are subsequently defined as the lines passing through thetranslated points on the reference plane 195.

Once the translated edge lines and translated points are defined on thereference plane, the original position of the tip of the missing cornerportion 175 can be estimated as the point 190 a at which the translatededge lines intersect on the reference plane 195. Dimensions of themissing portion 175 can then be determined using the translated pointsand point 190 a.

Alternatively, a plane which passes through cursor markers 180 a and 180c for each pair of cursor markers 180 a, c; 180 b, d defining an edge154, 155 of the blade 150 and is perpendicular to the reference plane195 is determined. The point defined by the intersection of all threeplanes is the intersection 190 a identifying the corner of the missingportion 175. Once the missing corner intersection 190 a is identified,measurements are taken in three dimensions from the remaining edgecursor markers 180 a, b, so that the measured dimensions of the missingportion 175 bounds are reasonably accurate despite the non-planarsurface of the blade 150.

FIG. 8 provides a general process flowchart of the method according tothe embodiments described above. The process begins 200 when an objectunder inspection is identified with a borescope. The borescope isaligned 210 with respect to the object under inspection, such as byusing a shadow 160 generated with the borescope or other knowntechniques for positioning the borescope substantially perpendicular tothe object under inspection. Once the borescope is aligned 210, theremaining edges of the object under inspection are identified withcursor markers 180 a-d, including the points immediately adjacent themissing portion on the remaining edges 152, 154, 155, and the missingportion 175 is defined 220 as described in the embodiments above. Themissing portion dimensions can then be determined 230 based upon thetwo- or three-dimensional position of the cursor markers 180 a-ddefining the missing portion area, as described above. The dimensions ofthe missing portion 175 are then produced 240 for display and theprocess is complete.

In an embodiment wherein the borescope is aligned 210, for example,using three-dimensional position of at least three points and a best-fitplane, the missing portion 175 dimensions are calculated with respect tothe best-fit plane. In a still further embodiment, the contour of theoriginal and remaining edges 158 can be determined automatically withoutidentifying points with cursor markers 185, such as using patternrecognition, so that once the borescope is aligned, a measurement of themissing portion dimensions is obtained.

As will be appreciated, the several embodiments of the inventiondescribed herein are particularly advantageous since the borescope isquickly aligned with the object under inspection and so the areacalculations are made in a known plane with a high degree of accuracy.Thus, a single inspection tool can be used to quickly and accuratelyobtain the area of a missing portion of an object under inspection,leading to reduced inspection times and more accurate determinations ofwhen service or repair is required on the object under inspection.

While the present invention has been described with references topreferred embodiments, various changes or substitutions may be made onthese embodiments by those ordinarily skilled in the art pertinent tothe present invention with out departing from the technical scope of thepresent invention.

The construction and arrangement of the borescope measurement apparatusand method, as described herein and shown in the appended figures, isillustrative only. Although only a few embodiments of the invention havebeen described in detail in this disclosure, those skilled in the artwho review this disclosure will readily appreciate that manymodifications are possible (e.g. variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, orientations, etc.)without materially departing from the novel teachings and advantages ofthe subject matter recited in the appended claims. Accordingly, all suchmodifications are intended to be included within the scope of thepresent invention as defined in the appended claims. The order orsequence of any process or method steps may be varied or re-sequencedaccording to alternative embodiments. In the claims, anymeans-plus-function clause is intended to cover the structures describedherein as performing the recited function and not only structuralequivalents but also equivalent structures. Other substitutions,modifications, changes and omissions may be made in the design,operating conditions and arrangement of the preferred and otherexemplary embodiments without departing from the spirit of theembodiments of the invention as expressed in the appended claims.Therefore, the technical scope of the present invention encompasses notonly those embodiments described above, but all that fall within thescope of the appended claims.

1. A method for determining with a borescope the dimensions of a missingcorner portion of an object under inspection, the object underinspection having remaining edges adjacent the missing portion, themethod comprising: aligning the borescope with the object underinspection for viewing a region containing the missing corner portion;capturing an image of the object under inspection including the missingcorner portion; placing first cursor markers on said image to identifypoints where the remaining edges of the object under inspection end andthe missing portion begins; placing at least one additional cursormarker on at least one of the remaining edges, defining a missingportion boundary with the first cursor markers and at least oneadditional cursor markers; and determining the missing portiondimensions using the missing portion boundary and first cursor markers.2. The method according to claim 1, wherein aligning the borescopecomprises projecting a pattern on the object under inspection, anddetermining a magnification parameter based upon the position of theprojected pattern in the image, wherein the magnification parameter isused in determining the dimensions of the missing corner portion.
 3. Themethod according to claim 1, wherein aligning the borescope comprisespositioning the borescope substantially perpendicular to a surface ofthe object under inspection.
 4. The method according to claim 1, whereinplacing at least one additional cursor marker comprises placing oneadditional cursor marker on each remaining edge and defining a missingportion boundary comprises generating lines from the first andadditional cursor markers on each respective remaining edge, anddetermining a position of an intersection of the lines.
 5. The methodaccording to claim 4, wherein determining the missing portion dimensionscomprises measuring a distance from each first cursor marker position tothe intersection of the lines.
 6. The method according to claim 5,wherein determining the missing portion dimensions further comprisescalculating the missing portion area defined by the missing portionboundary by subdividing the missing portion into geometric shapes,calculating the areas of the geometric shapes and summing the areas ofthe geometric shapes.
 7. The method according to claim 1, whereinplacing at least one additional cursor marker on the remaining edgescomprises placing one additional cursor marker on one of the remainingedges, and defining a missing portion boundary comprises: generating afirst line defined by the one of the first cursor markers located on thesame remaining edge as the one additional cursor marker; generating asecond line perpendicular to the first line extending from the other ofthe first cursor markers on the other remaining edge; adjusting thesecond line until the second line defines a missing edge of the otherremaining edge, the missing edge forming part of the missing portionboundary; and determining a position of an intersection of the first andsecond lines.
 8. The method according to claim 1, wherein placing atleast one additional cursor marker on the remaining edges comprisesplacing two additional cursor markers, one additional cursor marker oneach of the remaining edges, and defining a missing portion boundarycomprises: defining a best-fit reference plane using the first cursormarkers and two additional cursor markers; determining the position ofan intersection point on the best-fit plane corresponding to the missingtip of the missing corner portion; and defining the missing cornerportion boundary using the first cursor marker positions andintersection point.
 9. A method for determining with a borescope thedimensions of a missing corner portion of a blade, the blade havingremaining edges adjacent the missing portion, the method comprising:aligning the borescope with the blade; capturing an image of the bladeincluding the missing corner portion using the borescope; placing firstcursor markers on said image to identify points where the remainingedges of the blade end and the missing portion begins; placing at leastone additional cursor marker on at least one of the remaining edges,defining a missing portion boundary using the first cursor markers andat least one additional cursor markers; and calculating a length anddepth of the missing corner portion using the missing portion boundaryand first cursor markers.
 10. The method according to claim 9, whereinaligning the borescope comprises projecting a pattern on the blade, anddetermining a magnification parameter based upon the position of theprojected pattern in the image, wherein the magnification parameter isused in determining the dimensions of the missing corner portion. 11.The method according to claim 9, wherein aligning the borescopecomprises positioning the borescope substantially perpendicular to asurface of the blade.
 12. The method according to claim 9, whereinplacing at least one additional cursor marker comprises placing oneadditional cursor marker on each remaining edge of the blade anddefining a missing portion boundary comprises generating first andsecond lines from the first and additional cursor markers on eachrespective remaining edge, and defining an intersection of the lines.13. The method according to claim 12, wherein determining the missingportion dimensions comprises measuring a distance from each first cursormarker position to the intersection of the lines.
 14. The methodaccording to claim 9, wherein determining the missing portion dimensionsfurther comprises calculating the missing portion area defined by themissing portion boundary by subdividing the missing portion intogeometric shapes, calculating the areas of the geometric shapes andsumming the areas of the geometric shapes.
 15. The method according toclaim 9, wherein placing at least one additional cursor marker on theremaining edges comprises placing one additional cursor marker on one ofthe remaining edges and defining a missing portion boundary comprises:generating a first line defined by the one of the first cursor markerslocated on the same remaining edge as the one additional cursor marker;generating a second line perpendicular to the first line extending fromthe other of the first cursor markers on the other remaining edge;adjusting the second line until the second line defines a missing edgeof the other remaining edge, the missing edge forming part of themissing portion boundary; and generating an intersection of the firstand second lines.
 16. The method according to claim 9, wherein placingat least one additional cursor marker on the remaining edges comprisesplacing two additional cursor markers, one additional cursor marker oneach of the remaining edges, and defining a missing portion boundarycomprises: defining a best-fit plane using the first cursor markers andtwo additional cursor markers; calculating a first plane perpendicularto the best-fit plane and containing one of the first cursor markers andthe corresponding one of the additional cursor markers positioned on thesame one of the remaining edges; calculating a second planeperpendicular to the best-fit plane and containing the other of thefirst cursor markers and the corresponding other one of the additionalcursor markers positioned on the same remaining edge; determining anintersection point of the best-fit plane, the first plane and secondplane; and defining the missing portion boundary using the first cursormarker positions and intersection point.
 17. The method according toclaim 9, wherein the blade is a part of a turbo fan, turbo jet fan,compressor or turbine.
 18. A method for determining, with an inspectiondevice having an elongated inspection tube, the dimensions of a missingcorner portion of an object, the object having remaining edges adjacentthe missing portion said remaining edges being non perpendicular and nonparallel to each other, the method comprising: capturing an image usingsaid inspection device, said image including at least the portions ofsaid remaining edges adjacent said missing portion; identifying a firstposition along each of said remaining edges at which said remaining edgeends and said missing portion begins; defining an estimated corner pointrepresenting the point at which lines extended from each of saidremaining edges intersect; and displaying a measurement of the distancefrom the estimated corner point to the first position on one of saidremaining edges where said remaining edge ends and said missing portionbegins.